Glai: Of course there's a difference intreatment between bottom ported and sealed spkr designs... In the first place, the bottom ported model (should) have factored the distance between port & floor into the spkr design -- hence, for example Avalon (& others) supply specific devices WITH their spkrs (i.e., specific height fm floor)-- cones in the Eidolons' case. The distance fm the floor is set by the manufacturer... You can change the low frequency reproduction by changing that distance (i.e. using more or different supports) but that's another matter.
Incidentally, when I used Eidolons they sat directly onto the (marble in my case) floor with a coin protection -- just like you. Then I raised them simply by placing them directly on a concrete slab, slab on floor. Too complicated, and all I achieved was to hit a response at ~25 degrees fm the tweet.
In a sealed design things are a bit different and yr concern *would* be (i.e. again, theoretically) to DECOUPLE the spkr fm the floor mass -- but in a rigid way so as to avoid undue motion fm the spkr while playing...
I'm sure Avalon themselves could make recommendations -- not which specific PRODUCT/brand to use, but what TYPE of support: to couple, decouple, what type of material (soft, hard, etc)...
BTW, yr hard floor *should, in theory* contribute to good sonic results; good imaging, for one! Cheers
